Question: Why does Macbeth (or Lady Macbeth) change so dramatically over the course of the play?

Thesis: Macbeth changes into an evil ruler from a royal thane over the course of the play, as a result of the influence of Lady Macbeth, Macbeth’s blind ambition, and his excessive fear which eventually leads to his downfall at the end of the play.

Supporting Ideas:

1. Influence of Lady Macbeth
The influence of Macbeth's wife Lady Macbeth was the initial cause of the transformation that has occurred in Macbeth. Lady Macbeth seems to be even more ambitious than Macbeth at the beginning of the play; when Macbeth claims that he will no longer continue taking part in murdering the king, Lady Macbeth becomes outrageous and persuades him to change his mind.

Textual Evidence: (Act 1 Scene 7 Lines 80-81 I am settled, and bend up each corporal agent to this terrible feat.) (Act 1 Scene 5 lines 40-42 Come, you evil spirits that tend on mortal thoughts, unsex me here And fill me from the crown to the toe-top-full Of direst cruelty!)

2. Macbeth's blind ambition

Macbeth's blind ambition for power makes him commit more and more crimes; later, he is the one who plans Banquo's assassination with the three murderers without any help of Lady Macbeth.

Textual Evidence: (Act 3 Scene 3 Lines 42-27 There's comfort yet; they are assailable. Then be thou jocund. Ere the bat hath flown his cloistered flight, ere to black hecate's summons the shard-borne beetle with his drowsy hums hath rung night's yawning peal, there shall be done a deed of dreadful note.)

3. Macbeth's excessive fear
Macbeth's increasing fear and guilt following after consecutive murders are also the reason why he changes so dramatically over the course of the play; Macbeth sees the ghost of Banquo at the feast held in the palace, which seems to be a hallucination of Macbeth resulting from his excessive fear.

Textual Evidence: (Act 3.4 Lines 94 "Avaunt! and quit my sight! Let the earth hide thee! Thy bones are marrowless, thy blood is cold; Thou hast no speculation in those eyes which thou dost glare with!")